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Waterproof maps are maps that can be in direct contact with a considerable amount of water while still remaining completely usable. Waterproof maps are commonly used by hikers and others who need to navigate outdoors. They are best able to handle humidity and rain; complete submersion could result in some damage to some kinds of waterproof maps. A waterproof map is generally printed on waterproof paper and, if the map is not laminated, it is printed with waterproof ink that will not smudge or run when exposed to water. There are many different methods that can be used to produce a functional waterproof map.
The paper that the map is printed on is of the utmost importance. Normal paper, when exposed to water, becomes saturated and tears apart very easily. This obviously would not work for waterproof maps, as they need to remain functional even when exposed to water. In some cases, many maps are included in a book of maps; in such a case, it is common for only the front and back cover of the book to be waterproof.
There are two primary methods of waterproofing paper. Paper can be made with thick, tightly bound, water-repellent fibers that strongly resist water saturation. This tends to result in very strong, waterproof paper; however, only specialized inks can be used to mark such paper, generally leading to a higher overall cost. The other method is lamination; paper can be covered with a transparent, synthetic coating that repels water. Laminated maps can sometimes be stiff and unwieldy, though, and lamination does cost more money than printing on normal paper.
The ink used to produce waterproof maps is also extremely important. Regular dye ink is made from very small water-soluble particles; when exposed to water, they tend to smudge and run all over the page. Pigment inks, however, are made with larger particles that are not water soluble; once the ink saturates the paper, it dries and tends to smudge very little, if at all. Pigment inks and other, stronger inks are often used to produce waterproof maps. They are not necessary, however, when the paper that the map is printed on is laminated.
Waterproof maps are used by many individuals for professional and personal reasons. They are, for example, popular with military personnel because they can survive very harsh conditions and still remain usable. Outdoor enthusiasts also enjoy them very much for the same reasons. Waterproof topographical maps are very common; detailed geographical maps of an area are much more widely used outdoors in rainy conditions than political maps or atlases.